This invention concerns a method of calcining carbonaceous bodies, in particular electrodes, in either continuous or intermittent furnaces, and a containment structure for the implementation thereof.
Known are methods of calcining anodes in continuous furnaces. One of such prior methods (cfr. Published German Application DE-OS No. 3042708) provides for the carbonaceous blocks (anodes) to be covered with carbonaceous powder in order to protect them against oxidation, stowed into muffles, placed onto a truck, and pushed into the furnace in accordance with a preset thermal scheme.
During heating, and in particular in the temperature range of 300.degree. to 500.degree. C., there takes place a gaseous emission from the anodes of volatile organics issuing from the decomposition and/or distillation of a fraction of the binder forming the anode, in the gaseous, vapor, and particulate forms. Since the volatile substances comprise essentially aromatic hydrocarbons, said prior method has the drawback of being highly polluting.
To obviate such a drawback, a method has been proposed (cfr. European Patent Specification EP-OS No. 103130) wherein provisions are made for covering the carbonaceous bodies with an antioxidant protective powder and calcining them as moving through a truck furnace, in an oxidizing medium, which at the operating temperature, enables complete burning of the volatile substances within the furnace, and accordingly, the release of volatile-free gases.
However, since the carbonaceous bodies undergo in calcining an expansion due to the temperature increase, that prior method poses the problem that the electrodes distort, crack, and often open up on account of their contacting the truck walls, the rigid structure whereof opposes the expansion thrust.
Furthermore, owing to the chemical and physical changes undergone by the binder, pitch in this case, during calcination there form in the carbonaceous bodies cracks which deteriorate their mechanical and electrical properties.